When a circular knitting machine is in operation, frictional heat is generated between its components. The frictional heat causes thermal expansion and deformation of the components. Such expansion and deformation cause damage to knitting tools such as knitting needles and jacks, and brings about abnormalities of the needle selecting apparatus, producing pattern errors. This is a long-standing problem, which has become more serious in recent years. The speed of operation is increasing, and knitting machines are getting larger and larger, resulting in greater thermal friction. The increase in the use of electronic parts has also added to the amount of heat generation.
As a way of solving this problem, a number of methods for cooling the cylinder by air or water were proposed in the past.
For example, JP-A-4-245963 (1992) discloses a cylinder that is provided with a fluid path through which the air or fluid medium can flow to cool the cylinder. Forming a fluid path directly on the cylinder, however, entails a high manufacturing cost. It is also suspected that the direct cooling effect extends only to the cylinder, leaving the peripherals insufficiently cooled.
According to JP-A-6-287844 (1994) by the present applicant, an orifice is provided between the cylinder and the fabric in the lower part of the knitting section of the knitting machine to cool the cylinder and its peripherals as well as to remove and discharge fiber dust, etc. According to this prior invention, not only the cylinder but also the peripherals are cooled.
According to JP-A-10-60759 (1998), an annular air chamber is established between the cylinder and the dial, and a pressurized airflow is fed into it. The invention of this Japanese application was originally intended to provide an apparatus for preventing airborne cotton or dust, and the cooling of the knitting components per se is not mentioned at all in the specification. However, as long as an airflow is generated around the cylinder, a cooling effect on the cylinder would be expected. At first glance, this configuration resembles that of the present invention. Therefore, this prior apparatus will be discussed further in the section describing the effects of the prior apparatus by way of comparison with the present invention.